1. Field of the Invention
The present invention relates to a fixture for an abrasive cloth paper which is attachable with/detachable from a polishing base plate of a portable sander and on which an abrasive cloth paper is mounted, and more particularly to a fixture for the abrasive cloth paper applicable for a portable sander which performs polishing at an end portion of the polishing base plate.
2. Description of the Related Art
Various portable sanders have been used to correspond to diversified polishing works conventionally. A main body 2 of the portable sander 1 has a handle 3 and a configuration similar to household electric iron, to/from which a base plate 4 can be removably attached/detached. In some case, a portion of the base plate 4 to be mounted to the main body 2 of the sander is connected to a vibration generating source and in some case, polishing work is carried out just manually. A fixture attaching/detaching portion 5 for attachably/detachably holding the fixture on which a male member of the surface fastener is bonded via adhesive agent, is formed on the surface of an end portion of the base plate 4.
The fixture attaching/detaching portion 5 has a fixture mounting space 5a which is surrounded by rectangular wall portions and elongated longitudinally as understood from FIG. 1. On a rear wall face thereof is formed an engaging pawl 5b which is projected inwardly in a wedge shape and with/from which an end of the fixture is engaged/disengaged, and then an fastening hole 5c is formed from a front wall portion up to a front end surface of the base plate 4 for detachably supporting the other end of the fixture.
Typically, the fixture detachably mounted to the fixture attaching/detaching portion 5 of the base plate 4 is a rectangular block having a substantially eggplant-like section and similar to a configuration of the fixture 10 of the present invention shown in FIG. 1. What is different from FIG. 1 is that a surface of the fastening portion on which a surface fastener is wound and bonded integrally is just a smooth plane. On the surface of the fastening portion of this fixture is bonded a male surface fastener made of fiber well known conventionally or a molded surface fastener of synthetic resin having a plurality of hook-shaped engaging elements formed integrally on a surface of a plate-like substrate with adhesive agent. Then, a pile member (female surface fastener) formed on a rear surface of an abrasive cloth paper is fastened to a fastening surface having the hook-shaped engaging elements of the surface fastener bonded to the fixture 10, thus the abrasive cloth paper is fastened thereto.
However, the configuration of the aforementioned fixture is only an example, and may have various configuration corresponding to a surface shape of a product to be polished, and the fastening portion on which a surface fastener is to be mounted has not only an arc-shaped section as shown in FIG. 1, but also a substantially triangular section, a substantially inverse triangle section, a section in which a bottom portion of a triangular section is curved outward or inward in an arc shape or the like. Bonding and fixing of the surface fastener onto a fixture having such a diversified surface shape of the fastening portion is very troublesome and particularly if the surface of the fastening portion is in a complicated configuration, it is very difficult to fasten the surface fastener to an entire surface of the fastening portion accurately, so that often the surface fastener is bonded such that part thereof is floated.
Regardless of whether the surface fastener is made of fiber or molded of synthetic resin, when it is bonded to the surface of the fastening portion of the fixture, it only has to be bonded firmly to portions directly related to polishing in standpoint of shearing strength. In other words, it is important that the portion related to polishing by the abrasive cloth paper has to be mounted securely on the fixture via the surface fastener. This means that hook-shaped engaging elements of the surface fastener only have to be formed at least on portions directly related to polishing by the abrasive cloth paper. However, when the conventional fixture is used, as described above, the surface fastener has to be bonded and fixed on an entire surface of the fastening portion of the fixture, and at this time of bonding, deflection of position is likely to occur. Thus, to cope with such a phenomenon, the hook-shaped engaging elements need to be formed on a portion of the substrate where the elements may be unnecessary.
Accordingly, the present invention has been accomplished to solve such a conventional problem, and therefore it is an object of the invention to provide a fixture for an abrasive cloth paper in which a surface fastener does not have to be bonded prior to fixing of the abrasive cloth paper onto the fixture and in which hook-shaped engaging elements are disposed accurately at a portion directly related to polishing by an abrasive cloth paper fastening portion of the fixture with precedence.
According to an aspect of the present invention, there is provided a fixture for an abrasive cloth paper comprising a mounting portion which is attachable with/detachable from a base plate of a sander and a fastening portion on which the abrasive cloth paper is wound and fastened. And the fastening portion has a fastening surface in which a plurality of surface fastener engaging elements are formed integrally. With such a structure, a troublesome work for bonding the surface fastener to the fastening portion of the fixture via adhesive agent is eliminated and production cost is reduced thereby ensuring a very reasonable price.
Preferably, the surface fastener engaging element rows are composed of a plurality of hook-shaped engaging elements and reinforcement ribs are formed integrally on both sides of each hook-shaped engaging element. The abrasive cloth paper is fastened to the fastening portion of the fixture for polishing work. At this time, a very large force from multiple directions is applied to the hook-shaped engaging elements on which the abrasive cloth paper is fastened. Thus, the hook-shaped engaging elements are repeatedly bent so that breaking of their root portions often occurs. The aforementioned reinforcement rib reinforces particularly a stem portion of the hook-shaped engaging element so as to prevent breaking thereof due to repeated bending.
Further preferably, the fastening surface is composed of a plurality of surface fastener engaging element rows each including a plurality of hook-shaped engaging elements having the same directivity, arranged in parallel to a direction of winding of the abrasive cloth paper and the fastening surface includes surface fastener engaging element rows in which the direction of hooks are opposite. Because the direction of the hook of the hook-shaped engaging elements constituting part of the plurality of surface fastener engaging element rows is made opposite to that of the hook of the hook-shaped engaging elements constituting other surface fastener engaging element rows, a required fastening force with respect to the abrasive cloth paper resisting a large force applied from multiple directions as mentioned above is ensured.
Preferably, the fastening surface is formed not on the entire region of the fastening portion but a region in which the fastening surface does not exist is provided in part of the fastening portion. Although a part of the abrasive cloth paper most contributing to polishing at the polishing time has to be firmly fixed on the fixture, the other part only has to be just fixed to the fixture. Thus, the surface fastener engaging element rows don""t have to be disposed on a portion not related directly to polishing by the fixture. Such a structure can be achieved easily by forming the surface fastener engaging element rows integrally with the fixture. Meanwhile, the region in which the fastening surface does not exist can be formed arbitrarily based on other reasons than the aforementioned reason.
Also preferably, the fastening portion of the fixture includes a hollow portion inside thereof. Because the fixture is usually made of hard synthetic resin or rubber, it strikes a surface to be polished too strongly at the polishing time. Thus, the aforementioned hollow portion is formed so as to apply a predetermined elasticity to, at least, a fastening portion most related to polishing. The degree of the elasticity can be adjusted depending on a size of the hollow portion.
And preferably, the mounting portion includes a pair of engaging protrusions which are protruded in opposite directions to each other and a through hole is formed in the vicinity of each of the engaging protrusions in a direction perpendicular to the protruding direction of the engaging protrusion. This through hole applies a required elasticity in the vicinity of the engaging protrusion of the mounting portion like the aforementioned hollow portion and allows the engaging protrusion to be engaged with/disengaged from the mounting portion of the base plate.